Method of burning powdered coal



March 6, 1928.

. 1,661,408 w. B. CHAPMAN,

METHOD OF BURNING POWDERED COAL Filed July 21, 1921 i l AIR PREHEATER -1 "A I dwvwamtoz 53%;; flame/ 4 Kim M rWW4! Patented Mar. 6, 192 8.

UNITED STATES PATENT OFFICE.

WILLIAM B. CHAIRMAN, OF NEW YORK, Y., ASSIGN'OR TO CHAPMAN ENGINEERING COMPANY, OF MOUNT VERNON, OHIO, A CORPQRATION OF OHIO.

ma'rnon or BURNING rownnnru) COAL.

Application filed July 21,

The invention has for an object to provide a method of feeding powdered coal to any desired heating device in such manner that substantially complete combustion of all the carbonaceous fuel particles will be obtained.

In its preferred form the invention auto matically segregates, so to speak, the larger fuel particles from the smaller, whereby the small pieces-of coal which ignite and burn relatively quickly are quickly carried over to .the point of utilization of the heat, while thelarger fuel particles whichigmte and burn with greater difliculty are automatically afforded a longer period within which. they may be i nited or kindled and completely burned be ore passing out of the region within which complete combustion may be effected. Thus the necessity s avoided of employing coal of extremely fine and uniform-pulverization..

Further objects and advantages of the 1nvention will be in part obvious and in part specifically pointed'out. in the description herein contained, which, taken in con unc tion with the accompanying drawings, discloses certain preferred embodiments thereof; such embodiments, however, are to be considered merely as illustrative of its principle. In the drawing:

The single figure illustratesin section and somewhat diagrammatically an apparatus adapted to operate in accordance with the invention. 3 i

If owdered or pulverized coal be employe as a fuel for a heating apparatus, the combustion of the fuel is liable to be incomplete and inefiicient, due to the fact that the fuel particles tend to pass out of the region of combustion before being completely burned; this is particularly the case if the fuel is fed at high velocity into a small combustion chamber so that itremains in a region hot enought'o burn it, and provided with sufiicient air to burn 1t, only for a short period- The heavier pleces of ,coal especially pass relatively quickly from. the region within which ignition of such pieces may be effected, and if the fuel has a comparatively large moisture content the contact between the same and the hot gases which are to cause combustion may be insufficient toinsrn that the fuel particles will be completely burned. Thus fuel of the 1921. Serial No. 486,353.'

above naturehas had to be exceedingly fine and uniform verization.

According to the present invention, the air which 1s to support combustion is formed into a moving column and the powdered coal is fed into .said column, the velocity of the air being so proportioned'with regard to the fineness of the coal that the latter is carried along with the air to the combustion chamber or point of utilization of the heat. Thus the coal is floated, so to speak, by the air column, and is supported by the air until it burns, and therefore the fuel particles do not pass through the region of combustion at such a high rate of speed as would have to be the case if their own velocity of feed were reliedupon to project them into the region of combustion, and the fuel need not be pulverized either so finely or so uniformly to obtain efficient combustion.

Preferably the powdered coal, is fed into the air column in a direction substantially opposed to the direction of travel of the air, and thus the smaller fuel particles are quickly carried along with the air to the combustion chamber or point of utilization of heat, while the lar er particles penetrate further into the air co umn until the velocity egree of pulof the latter arrests their motion and carries feed the powdered coal into the upper portion'of such column, the point of feed of the particles, the depth of the air column and its velocity being-so proportioned to each other that substantially all of the small and large fuel particles will be carried along with the air as above described.

Referring to the drawing, I have shown a heating apparatus having a substantially vertical air conduit 1, theconduit having such depth and area and the air being carried into the lowenend of the conduit with such velocity, that pulverized coal particles dropping into the conduit will be lifted and carried along to the point of utilization of the heat, for example, a combustion chamber 2, indicated at the left of the figure. For any given furnace the amount of coal necessary to be fed in to produce the required amount of heat, may be determined,

round to an;

also the amount of air necessary for the proper combustion of this quantity of coal. The minimum velocity in the air column necessary to support the size of coal to be employed, will also be known, and thus for any given installation the size of conduit 1 to be employed may be determined from the above factors. In other words, the size of the. conduit 1 should be such that the air necessary for the proper combustion of the amount of fuel to be employed, will travel through the conduit at such velocity as to support and carry along the fuel particles in all parts of the conduit.

The fuel may be fed into the air conduit 1 by merns of a spout or the lilre. 3 extending through an opening 4 in the side wall 5 of the conduit, and containing a suitable feeding device such as worm (l. whichcarries the coal from a hopper 7 to the mouth of the. spout 3 from, whence the coal drops by gravity into contact with the upwardly moving air column. The fuel is then carried along with the air column until the heat within the combustion chamber 2 raises it to ignition temperature. in most instances, the flames from combustion chamber 2 will ex tend back far enough to reach the fuel as the latter is fed into air conduit. 1, and thus the particles of coal pass through a sheet of flame which may e sufficient to start their combustion at once. \Vhen the fuel particles begin to burn, the resulting gaseous expan- .on accelerates the movement of the burning particles over into the combustion chamber 2. thus facilitating the operation of carrying the powdered coal along to the point where its heat is to be utilized. The fine particles which burn quickly are readily picked up by the aircolumn and their combustion may easily be completed within chamber 2 before they pass out of the zone in which their heat may be utilized. The larger or heavier fuel particles may also be ignited by the flames at the upper end of air conduit 1, but will tend to penetrate further into the air column until they burn sufficiently to enable their reduced mass and the expanding gases surrounding them to carry them along with the air into the combustion chamber. Thus a longer period of time is afforded for the larger particles to ignite and -burn completely before they pass out of the zone within chamber 2, wherein their-comlnistion may be completed.

I prefer to preheat theair before it enters the lower end of conduit 1 to a temperature sufficient to ignite the fuel particles when the same are brought into proper contact therewith as by an air preheater 8 shown diagrammatically inthe drawing, and which may be of any suitable type. Thus when fuel particles fall by gravity into the con- (luit 1 in opposition to the upward motion of the preheated air therethrough, the resultant heating of the-particles will assist in igniting them, and the smaller or dry particles will be quicklyignited and carried along to the point of utilization of the heat, whereas the heavier or wetter fuel particles will dro :further into the conduit 1; the length of suc i conduit and the velocity of the air passing therethrough being so regulated with reference to the fuel fed that substantially all the fuel particles will be ignited. \Vhen ignition of the fuel particles begins, the resulting expansion of the burning gases accelerates the movement of the same over into the'coinbustion chamber 2 as previously described. Thus the particles are kindled or. ignited within the conduit 1, and are carried along to combustion chamber 2 where their combustion is com leted. \Vhen the air is reheated in the a ove manner, the initial ve locity of the air column may be relatively less, since the ignition ofthe fuel particles assists materially in producing a current strong enough to carry the burning particles along to the combustion chamber.

Furthermore. it will be noted that the small fuel particles ignite quickly and pass along with the air column while the large fuel particles drop down further into the conduit aml are thus automatically afforded a longer period of contact with the preheated air until ignition occurs. This prolonged period of contact with the preheated air also insures that the lar e fuel particles will have time enough to iurn completely before they pass out of the zone within coinbustion chamber .2 in which their combustion may be completed. This is an important feature of the invention since the necessity is thereby avoided of pulverizing the coal exceedingly fine to prevent the larger particles from passing out of the region where combustion may be effected before ignition takes place, or from coming into contact with the material being heated before combustion is completed. In other words, according to the present invention fuel of non-uniform size or-quality may be efficiently burned owing to the fact that the invention automatically heats each particle sufficiently to kindle it before reaching the combustion chamber, and affords each particle sutlicient time to burn completely before it passes out of the region wherein its heat may be utilized or its combustion completed.

The point from which the fuel is fed into the column of preheated air, or the level from which the coal is .dropped, may be varied according to the conditions. The spout 3 being located below the top of conduit 1, is particularly adapted for use when small or dry fuel particles are employed, such fuel being easily ignited, and thus the short period of contact which is afforded between the fuel issuing from spout 3 and the preheated air column, will be sufficient to bring about ig- 111t0 conduit 1 from the level of the of the apparatus by means of a spout 3"and percentage oflarge or wet pieces, or i ,nition before theparticle's remain very lo I in theconduit. 1. The coal may be droppe drawings, a spout'3", similar to thes out} 3 previously described feed the coal from a chamber 10 above con duit 1 As the large pre- - viously-fed burning fuel particles for a relatively longer period of time, whereby large or wet pieces may be .more intensely heated to ignite them. t l

While certain specific embodiments of the invention have been described, it is obvious that many changes may be made therein without departing from the-spirit oftlie invcntiomas definedin the following claims.

I claim:.

1. The method of burning powdered coal,

which consists informing'outside of the combustion chamber proper an upwardly directed confined column of preheated air which consists in forming of restricted particles, feeding powdered coal into such column and igniting-the fuel therein, whereby the said column willflarrest the fall of substantially all the fuel particles and prevent them from escaping without being igor-wet fuel particles. fall from the spout 3*, they will be subjected I to the heat of the air column and the area moving with sufficient ve-- 'locity to support substantially all thefu'elcombustion chamber proper an upwardly di-.

rected confined column-of air moving with suflieient velocity all the .fige'l particles,

passing thekindled fuel and aiij into the combustion chamber-proper, may be locatedaove the roof 9 of the'apparatus and positioned to.

-3.; The method. of. burning powdered coal which consists in -fo rming outside of the combustion chamber proper an upwardly direeped confinedcolumn of air of restrict edar ea and moving with suflicient velocity to support substantially all the fuel particles,

feeding powdered coal by gravity into such column,

to support substantially feeding. powdered coal through a flame mtosuch column and ignit -i ingthe fuel therein, whereby the said col- -uIIm -will arrest the fall. of substantially all the fuel particles and prevent them from escaping without being ignited, and'then whereby the latter 1 will arrest the fall, of substantially all the. fuel particles and being ignited, and then passing the kindled fuel and air into the combustion chamber proper.

fuel and air into the combustion chamber P 'QP c Iu'testimony that I claim the foregoing, I have hereunto set my hand'this 8th day of July, 1921. I

WILLIAM B. CHAPMAN.

prevent them j from, escaping without 1 proper :4. The method of burning powdered coal feeding powdered coal into such i 

